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Do not emit invalid suggestion in E0191 when spans overlap #115077

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Merged
merged 2 commits into from
Aug 22, 2023
Merged

Do not emit invalid suggestion in E0191 when spans overlap #115077

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bf766cd
Add test for #115019
estebank Aug 21, 2023
b86285a
Do not emit invalid suggestion in E0191 when spans overlap
estebank Aug 21, 2023
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16 changes: 15 additions & 1 deletion compiler/rustc_hir_analysis/src/astconv/errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -597,7 +597,21 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
}
}
if !suggestions.is_empty() {
suggestions.sort_by_key(|&(span, _)| span);
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@compiler-errors compiler-errors Aug 21, 2023 •
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Are you certain that the suggestion spans will end up sorted in such a way that two non-adjacent keys never overlap? If not, then since this is the error path, I feel like it may just be easier to do the O(N^2) full pairwise comparison here.

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SpanData manually implements Ord on (lo, hi, ctxt). That means that by sorting any two adjacent spans that don't overlap imply that the spans further apart from each other also don't overlap.

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@compiler-errors compiler-errors Aug 21, 2023 •
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What about spans that overlap only at their end? Like spans that look like: [(1, 5), (2, 3), (4, 5)], where the first and last elements overlap?

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@compiler-errors compiler-errors Aug 21, 2023 •
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Wait, maybe it doesn't matter, since by construction that would imply any intermediate spans overlap. Idk.

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Your last comment is exactly right.

// There are cases where one bound points to a span within another bound's span, like when
// you have code like the following (#115019), so we skip providing a suggestion in those
// cases to avoid having a malformed suggestion.
//
// pub struct Flatten<I> {
// inner: <IntoIterator<Item: IntoIterator<Item: >>::IntoIterator as Item>::core,
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// | ^^^^^^^^^^^^^^^^^^^^^
// | |
// | associated types `Item`, `IntoIter` must be specified
// associated types `Item`, `IntoIter` must be specified
// }
let overlaps = suggestions.windows(2).any(|pair| pair[0].0.overlaps(pair[1].0));
if !suggestions.is_empty() && !overlaps {
err.multipart_suggestion(
format!("specify the associated type{}", pluralize!(types_count)),
suggestions,
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12 changes: 12 additions & 0 deletions tests/ui/associated-type-bounds/overlaping-bound-suggestion.rs
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@@ -0,0 +1,12 @@
#![allow(bare_trait_objects)]
#![feature(associated_type_bounds)]
trait Item {
type Core;
}
pub struct Flatten<I> {
inner: <IntoIterator<Item: IntoIterator<Item: >>::IntoIterator as Item>::Core,
//~^ ERROR E0191
//~| ERROR E0223
}

fn main() {}
24 changes: 24 additions & 0 deletions tests/ui/associated-type-bounds/overlaping-bound-suggestion.stderr
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@@ -0,0 +1,24 @@
error[E0191]: the value of the associated types `IntoIter` (from trait `IntoIterator`), `IntoIter` (from trait `IntoIterator`), `Item` (from trait `IntoIterator`), `Item` (from trait `IntoIterator`) must be specified
--> $DIR/overlaping-bound-suggestion.rs:7:13
|
LL | inner: <IntoIterator<Item: IntoIterator<Item: >>::IntoIterator as Item>::Core,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| | |
| | associated types `Item`, `IntoIter` must be specified
| associated types `Item`, `IntoIter` must be specified

error[E0223]: ambiguous associated type
--> $DIR/overlaping-bound-suggestion.rs:7:13
|
LL | inner: <IntoIterator<Item: IntoIterator<Item: >>::IntoIterator as Item>::Core,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: if there were a trait named `Example` with associated type `IntoIterator` implemented for `(dyn IntoIterator + 'static)`, you could use the fully-qualified path
|
LL | inner: <<(dyn IntoIterator + 'static) as Example>::IntoIterator as Item>::Core,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0191, E0223.
For more information about an error, try `rustc --explain E0191`.